Radio frequency identification (RFID) technology comprises a non-contact automatic identification system. RFID technology provides an automatic method for efficiently collecting product, place, time or transaction data without human intervention.
As shown in FIG. 1, an RFID system 100 generally comprises a host computer system 110 and at least one reader unit 120. The reader unit 120 may communicate with the host computer system 110 via wired or wireless communication. The reader unit 120 uses an antenna to transmit radio energy to interrogate a responder such as a radio frequency identification (RFID) tag. The RFID system 100 shown in FIG. 1 comprises a first RFID tag 130, a second RFID tag 140, and an Nth RFID tag 150.
An RFID tag (e.g., RFID tag 130) does not have an on-chip battery, but rather receives its energy from the incoming RF signal from the reader unit 120. The RFID tag 130 uses the energy from the incoming RF signal to extract the data that is stored in the chip of the RFID tag 130 and send the data back to the reader unit 120. The reader unit 120 can then send the data from the RFID tag 130 to the host computer system 110 for further processing.
An RFID system usually comprises at least one reader unit and a plurality of RFID tags. An RFID system can be used to identify persons or objects that have an RFID tag and that are located within the reading range of reader unit. The reader unit uses a pre-defined RFID communication protocol to communicate with all of the RFID tags that are located within range.
In one embodiment of an RFID system the reader unit transmits data to an RFID tag with an amplitude modulated (AM) radio frequency (RF) signal having a frequency in the range from nine hundred MegaHertz (900 MHz) to two and fourth tenths GigaHertz (2.4 GHz). In the RFID tag a demodulator recovers the baseband signal from the incoming RF signal. A demodulator in an RFID tag should be able to recover the baseband signal of an RF amplitude that has sufficient power to power the chip of the RFID tag.
The demodulator in an RFID tag should also be able to decode amplitude shift keying (ASK) demodulation depths from twenty percent (20%) to one hundred percent (100%). The demodulator in an RFID tag should also be able to receive data at data rates that range from sixteen thousand bits per second (16 Kbps) to eighty thousand bit per second (80 Kbps) or higher.
An exemplary prior art RFID tag 200 is shown in FIG. 2. The RFID tag 200 comprises an analog block 210, a digital state machine block 220, and a non volatile memory (NVM) block 230. The analog block 210 comprises a demodulator circuit 215 and a modulator circuit 225. Radio frequency (RF) energy couples to the elements of the RFID tag 200 through antenna 235. On-chip direct current (DC) power is generated in RFID tag 200 using a charge pump circuit (not shown in FIG. 2). The DC power is used to power the remaining functions of the chip of RFID tag 200.
Data detection, voltage regulation, backscatter clock generation, and other functions are performed in the analog domain of analog block 210. The actual protocol functions are handled in the digital state machine block 220. EPC data or user data may be stored either in the non-volatile memory (NVM) block 230 or in a laser read only memory (ROM) unit (not shown in FIG. 2).
The functions of direct current (DC) power generation, clock signal generation, demodulation, etc. are performed using the analog circuitry in the analog block 210. The digital state machine block 220 performs an RFID communication protocol function with the RFID reader unit. The RFID communication protocol function is carried out in the digital state machine block 220.
The RFID communication protocol permits a single RFID tag to be singled out among all of the RFID tags in a system. The process of singling out a particular RFID tag is referred to as singulation. Singulation of a particular RFID tag is usually achieved by using the unique RFID tag identifier that is embedded in each RFID tag.
The RFID communication protocol regulates the sending of commands from the reader unit to the RFID tags. The RFID communication protocol allows command to be executed in specific states of the RFID tags. Commands are classified as mandatory commands, optional commands, and proprietary commands. Mandatory commands allow general and operational control of the RFID tags. Optional commands may or may not be executed by the RFID tags. Proprietary commands are designed to provide unique features and functions to be executed by the RFID tags.
RFID communication protocol commands are further classified as global commands and singulated commands. Global commands may be executed by any active RFID tag in the system. Singulated commands may be executed only by the RFID tag that is currently singulated (i.e., singled out from the other RFID tags).
As shown in FIG. 2, RFID tag 200 also comprises a data logger 240 and an on-chip sensor unit 250. A first example of an on-chip sensor unit 250 is a temperature sensor. A second example of an on-chip sensor unit 250 is a pressure sensor. The sensor unit 250 provides sensor information to the digital state machine block 220 through the data logger 240.
The data logger 240 is capable of receiving and storing sensor information from one or more on-chip sensor units 250. The on-chip sensor units 250 periodically send sensor information to the data logger 240. The data logger 240 comprises data logger registers 260 and a data logger memory 270. The data logger 240 stores information from the sensor units 250 in logger memory 270 to record a history of the sensor information that is detected by the on-chip sensor units 250. The data logger 240 is located between the digital state machine block 220 and the sensor units 250.
FIG. 3 illustrates a diagram showing an exemplary data logger memory 240. As previously mentioned, data logger 240 comprises data logger registers 260 and data logger memory 270. In one embodiment of data logger 240 the total number of memory locations in the data logger registers 260 and the data logger memory 270 is sixty four thousand bytes (64 Kbytes).
In the architecture of prior art RFID system 100 there are no specific commands in the RFID communication protocol for the RFID reader 120 to use to communicate with a data logger 240 in a prior art RFID tag. The RFID communication commands that presently exist in the RFID communication protocol are supposed to be used in a modified form to communicate with the data logger 240.
There is a need in the art for an RFID reader that is capable of communicating with a data logger in an integrated RFID tag. There is also a need in the art for an RFID reader that is capable of communicating with sensor units in an integrated RFID tag by communicating with the data logger of the integrated RFID tag.
Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior uses, as well as future uses, of such defined words and phrases.